Power supply circuit for measuring transient thermal resistances of semiconductor device

Abstract

A power supply circuit for measuring transient thermal resistances includes an inverter circuit provided on a primary side of a transformer and controlled by a PWM signal, a rectifier circuit provided on a secondary side of the transformer and including a DC reactor, and a control circuit controlling the PWM signal so as to output a pulsed output current from the rectifier circuit to a semiconductor device to be measured. The control circuit sets a first PWM frequency at rising timing of the output current, and sets a second PWM frequency when a predetermined time t1 elapses from the rising timing of the output current. The control circuit sets the first PWM frequency higher than the second PWM frequency.

What is claimed is: 
     
       1. A power supply circuit for measuring transient thermal resistances of a semiconductor device, comprising:
 a transformer; 
 an inverter circuit provided on a primary side of the transformer and controlled by a PWM signal; 
 a rectifier circuit provided on a secondary side of the transformer and including a DC reactor; and 
 a control circuit controlling the PWM signal so as to output a pulsed output current from the rectifier circuit to the semiconductor device to be measured, 
 wherein the pulsed output current output to the semiconductor device to be measured includes an individual current pulse defined by a rising edge and a falling edge, and 
 the control circuit sets a frequency of the PWM signal to a first PWM frequency at a timing of the rising edge of the individual current pulse, sets a frequency of the PWM signal to a second PWM frequency at timing when a predetermined time t 1  elapses from the timing of the rising edge of the individual current pulse, the predetermined time t 1  being less than a time between the rising edge and the falling edge of the individual current pulse, and sets the first PWM frequency to be higher than the second PWM frequency, thereby measuring the transient thermal resistances of the semiconductor device. 
 
     
     
       2. The power supply circuit for measuring transient thermal resistances of the semiconductor device according to  claim 1 , wherein the control circuit sets a frequency of the PWM signal to the first PWM frequency at the timing of the falling edge of the individual current pulse, and sets the first PWM frequency to be higher than the second PWM frequency. 
     
     
       3. A method of measuring transient thermal resistances of the semiconductor device, comprising:
 outputting a pulsed output current from an inverter circuit controlled by a PWM signal to the semiconductor device to be measured, the pulsed output current output to the semiconductor device to be measured including an individual current pulse defined by a rising edge and a falling edge; 
 setting a frequency of the PWM signal to a first PWM frequency at a timing of the rising edge of the individual current pulse; and 
 setting a frequency of the PWM signal to a second PWM frequency at timing when a predetermined time t 1  elapses from the timing of the rising edge of the individual current pulse, the predetermined time t 1  being less than a time between the rising edge and the falling edge of the individual current pulse, wherein the first PWM frequency is higher than the second PWM frequency. 
 
     
     
       4. The method of measuring transient thermal resistances of a semiconductor device according to  claim 3 , further comprising setting a frequency of the PWM signal to the first PWM frequency at the timing of the falling edge of the individual current pulse, wherein the first PWM frequency is higher than the second PWM frequency.